Perpendicular magnetic recording (PMR) write head with improved shapes of side shield and main pole

ABSTRACT

A perpendicular magnetic recording writer is disclosed with a side shield separated from a write pole side by a gap layer at an air bearing surface (ABS) where the side shield has a first sidewall facing the write pole with an end at height (h 1 ) from the ABS, and a second sidewall at height h 1  that is parallel to the ABS. The write pole side is curved such that a first portion proximate to the ABS is at an angle of 0 to 40 degrees with respect to a center plane formed orthogonal to the ABS, and a second section proximate to a corner where the curved side connects with a flared main pole side is formed substantially parallel to the second sidewall. When h 1  is 30-80 nm, and the corner is 80-150 nm from the ABS, overwrite is improved while cross-track field gradient is enhanced.

This is a Divisional application of U.S. patent application Ser. No.14/819,534, filed on Aug. 6, 2015, which is herein incorporated byreference in its entirety, and assigned to a common assignee.

RELATED PATENT APPLICATIONS

This application is related to the following: U.S. Pat. No. 9,361,912;and U.S. Pat. No. 9,299,367; both assigned to a common assignee andherein incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a PMR write head wherein the main polehas a greater volume within 150 nm of the air bearing surface (ABS) byincreasing the curvature on the narrow write pole portion at the ABS andshrinking the height of the side shield portions facing the write poleto less than 80 nm thereby reducing internal flux leakage from main poleto side shields, improving overwrite (OW), and enhancing the cross-trackfield gradient.

BACKGROUND

A PMR write head typically has a main pole with a small surface area atan air bearing surface (ABS), and coils that conduct a current andgenerate a magnetic flux in the main pole such that the magnetic fluxexits through a write pole tip and enters a magnetic medium (disk)adjacent to the ABS. Magnetic flux is used to write a selected number ofbits in the magnetic medium and typically returns to the main polethrough two pathways including a trailing loop and a leading loop. Thetrailing loop generally has a trailing shield structure separated fromthe main pole by a write gap, and the leading loop includes the leadingshield that is separated from the main pole by a leading gap. Sideshields are relied on to enhance the cross-track field gradient.

Shingled magnetic recording (SMR) is a form of PMR and has been proposedfor future high density magnetic recording by R. Wood et al. in “TheFeasibility of Magnetic Recording at 10 Terabits Per Square Inch onConventional Media”, IEEE Trans. Magn., Vol. 45, pp. 917-923 (2009). Inthis scheme, tracks are written in a sequential manner from an innerdiameter (ID) to an outer diameter (OD), from OD to ID, or from OD andID towards a middle diameter (MD) in a radial region of a disk in a harddisk drive (HDD). In other words, a first track is partially overwrittenon one side when a second track adjacent to the first track is written,and subsequently a third track is written that partially overwrites thesecond track, and so forth. Track widths are defined by the squeezeposition or amount of overwrite on the next track rather than by thewrite pole width as is the case in today's hard drives.

One of the main advantages of shingled writing is that write pole widthno longer needs to scale with the written track width. Thus, theopportunity for improved writability and higher device yield is notrestricted by using pole width as a critical dimension to be tightlycontrolled. Secondly, adjacent track erasure (ATE) becomes less of anissue because tracks are written sequentially in a cross-track dimensionand only experience a one time squeeze from the next track.

In today's PMR writer design, the geometries and dimensions of the mainpole and side shields are key factors for both overwrite and dBER (deltabit error rate) performance in hard disk drives (HDD). In a fullycoupled shield (FCS) where the trailing shield, leading shield, and sideshields completely surround the main pole at the ABS, the side shieldsare first plated on the leading shield, then a conformal non-magneticmaterial is deposited to form a leading gap and side gaps on the exposedsurface of leading shield, and sidewalls of the side shields,respectively. Next, the main pole is plated on the leading gap and sidegaps. As a result, the main pole shape proximate to the ABS is mainlydefined by the shape of adjacent portions of the side shields. There isalways flux leakage between the side shields and main pole due to thinside gaps in current writer designs. A write head that can deliver orpack higher bits per inch (BPI) and higher tracks per inch (TPI) isessential to the area density improvement. If writeability can besustained, the main pole size must shrink, and a thinner write gap atthe main pole trailing (top) surface and a narrower side gap adjoiningthe main pole sides in the cross-track direction are preferred forbetter track field gradient (Hy_grad, BPI) and cross-track fieldgradient (Hy_grad_x, TPI), respectively. However, with extremely narrowmagnetic spacing between the main pole and surrounding shields, internalflux shunting becomes severe and is the major factor for a dramaticdecrease in OW and writability degradation.

Therefore, a new side shield and main pole design is needed to minimizeinternal flux shunting in order to provide improved writability whilemaintaining high TPI capability for advanced writers with thin sidegaps.

SUMMARY

One objective of the present disclosure is to provide a main pole andside shield structure for a PMR writer that minimizes internal fluxshunting to enable better writability while maintaining an excellentcross-track field gradient for side shield heights less than 80 nm.

Another objective of the present disclosure is to provide a method ofmaking the main pole and side shield structure of the first objective.

According to one embodiment of the present disclosure, these objectivesare achieved by forming a side shield made of a 10-16 kG magnetic layeron each side of a main pole in a cross-track direction at the ABS. Eachside shield has a sidewall facing the main pole wherein a first sidewallsection extends from the ABS at an angle γ of 0 to 40 degrees withrespect to a center plane that bisects the main pole, and to a firstheight of 30 to 80 nm. There is a second sidewall section connected toan end of the first sidewall section at the first height, and formedsubstantially parallel to the ABS. The second sidewall section has across-track width of 20 to 300 nm and connects with a third sidewallsection that extends to a side of the side shield. The main pole has anarrow front portion called a write pole at the ABS, and a wide backportion that adjoins the back end of the write pole between two cornersat a third height from the ABS. Flared sides of the wide back portionextend from each of the two corners towards a back end of the PMRwriter, and are separated by increasing cross-track distance as thedistance from the ABS increases. The write pole preferably has acontinuously curved sidewall on each side of the center plane wherein afirst section of curved sidewall proximate to the ABS is formed at theangle γ, and a second section of curved sidewall proximate to eachcorner is formed at an angle that is 90±5 degrees with respect to thecenter plane. As a result, the write gap thickness between the firstsidewall section of side shield and first section of write pole curvedsidewall is substantially the same as that of the write gap portionbetween the second sidewall section and the second section of curvedsidewall. Moreover, there is less coupling between the main pole andside shields to minimize internal flux shunting, and the main polecorners are formed closer to the ABS which means greater main polevolume proximate to the ABS and better writability.

In a second embodiment, each side shield may be a composite with aninner 19-24 kG magnetic (hot seed) layer adjoining the side gap on eachside of the center plane, and an outer 10-16 kG magnetic layer adjoininga side of the hot seed layer that faces away from the main pole.

A method for forming the side shield and main pole structure of thepresent disclosure is provided. A side shield magnetic layer may bedeposited on a substrate that corresponds to the leading shield. Then aphotoresist is coated on the side shield magnetic layer and patterned toform a masking layer with openings that expose regions of side shieldmagnetic layer to be removed in a subsequent etch process. A key featureis the use of optical proximity correction (OPC) features in thephotomask that may be chrome on quartz, which is employed for thepatternwise exposure of the photoresist layer. The photoresist layerbecomes a masking layer after patternwise exposure and development withan aqueous base solution, for example. In particular, opaque OPC shapesthat may be chrome features are added to the photomask at the junctionof an opening where a first chrome side formed at angle y to the centerplane intersects a second chrome side that is aligned orthogonal to thecenter plane. The added OPC shapes are responsible for avoidingexcessive rounding at the intersection of first and second sides of theopening in the patterned masking layer. Thereafter, an etch process suchas ion beam etching (IBE) is used to transfer the pattern in the maskinglayer through the side shield magnetic layer to generate side shields oneach side of the center plane, and an opening between the side shieldswherein the main pole will be formed. As a result, the first and secondchrome sides on the photomask are responsible for forming the first andsecond sidewall sections, respectively, in each side shield.

After the masking layer is removed, a gap layer is conformally depositedon the side shields and exposed surfaces of the leading shield to formside gaps and a leading gap, respectively. Then, the main pole is platedon the gap layer, and from a top-down view, generally conforms to theshape of the side shield sidewall in a region proximate to the ABS. Achemical mechanical polish (CMP) process may be performed to produce aplanar top (trailing) surface on the main pole that is coplanar with topsurfaces of the side gaps and side shields. Then, the trailing shieldand remainder of the write head may be fabricated by a conventionalsequence of steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an ABS view of a PMR writer fabricated by the inventors usinga process of record (POR) wherein the trailing shield, side shields, andleading shield form an all wrap around (AWA) shield structure around themain pole.

FIG. 2a is a top-down view of the PMR writer in FIG. 1 wherein thetrailing shield and write gap are removed to depict the main pole andside shields.

FIG. 2b is a down-track cross-sectional view of the PMR writer in FIG.1.

FIG. 3 is a top-down view of a PMR writer wherein main pole and sideshield shapes are formed according to a first embodiment of the presentdisclosure.

FIG. 4 is an overlay of FIG. 3 on FIG. 2a that shows less main pole-sideshield coupling and a greater main pole volume proximate to an airbearing surface with the main pole and side shield design of the firstembodiment.

FIG. 5 is an ABS view of a PMR writer wherein a main pole and compositeside shields are formed according to a second embodiment of the presentdisclosure.

FIG. 6 is a top-down view of the PMR writer in FIG. 5 wherein thetrailing shield and write gap are removed to depict the main pole andcomposite side shields.

FIG. 7 is a down-track cross-sectional view of the PMR writer in FIG. 5.

FIG. 8 is a plot comparing Hy vs. erase width during AC mode for a PMRwriter having the POR structure in FIG. 2 with the first embodimentstructure in FIG. 3.

FIG. 9 is a plot comparing Hy grad x@5K Oe/nm vs. erase width during ACmode for a PMR writer having the POR structure in FIG. 2 with the firstembodiment structure shown in FIG. 3.

FIGS. 10 and 14-17 are ABS views depicting a sequence of steps employedto fabricate a main pole and side shield structure according to a firstembodiment of the present disclosure.

FIG. 11 is a top-down view of a photomask design with OPC features thatis used to fabricate the side shield structure according to a firstembodiment.

FIGS. 12-13 are top-down views showing intermediate process steps duringthe fabrication of the main pole and side shields according to the firstembodiment.

DETAILED DESCRIPTION

The present disclosure relates to a PMR writer with a side shield andmain pole structure proximate to the ABS that minimizes internal fluxshunting from the main pole to surrounding side shields, and enables alarger main pole volume within 150 nm of the ABS. The main pole may haveone or both of a tapered leading side and tapered trailing side. The PMRwriter may have a combined read head/write head structure as previouslydescribed in related U.S. Pat. No. 9,361,912. Moreover, the main poleand side shield structures of the present disclosure are not limited toa particular write head design, and are compatible with either anon-double write shield (non-DWS) or double write shield (DWS)configuration as described in the aforementioned related patentapplication. In the drawings, the y-axis is a cross-track direction, thez-axis is a down-track direction, and the x-axis is in a directionorthogonal to the ABS and towards a back end of the device.

Referring to FIG. 1, an ABS view of a fully coupled shield (FCS) alsoknown as an all wrap around (AWA) shield design currently fabricated bythe inventors is shown wherein a main pole has a front portion referredto as a write pole with a medium facing side 14 comprised of leadingedge 14 b, and a trailing edge 14 t which defines a track width TW. Themain pole extends behind the plane of the ABS to a back portion (notshown) that is magnetically connected to the trailing shield comprisedof an upper 16-19 kG magnetic layer 20 b and a 19-24 kG hot seed layer20 a where the hot seed layer and write gap 17 b have a cross-trackwidth b. The write gap has thickness a.

Side shields 19 s are made of a 10-16 kG magnetic layer, have adown-track thickness v, and are separated from the write pole by a sidegap 17 s having a cross-track width d. Each side shield has a topsurface that adjoins trailing shield layer 20 b between a side 17 e ofthe write gap and a side 60 (or 61) of the side shield. There is also aleading shield 34, which is separated from leading edge 14 b by a leadgap 17 a. The leading shield adjoins the side shields, and with the16-19 kG magnetic layer 20 b thereby forms an AWA shield design toimprove field gradients in the down-track and cross-track directions aswell as adjacent track erasure (ATE) performance.

FIG. 2a shows a top-down view of the side shield and main pole structurein FIG. 1 with the trailing shield and write gap removed. The main poleand side shields have a process of record (POR) design. Center plane44-44 bisects the main pole including a back portion 18 m and is alignedorthogonal to the ABS 30-30. A front portion of the main pole also knownas the write pole 18 p has a trailing edge 14 t at the ABS, and has acurved sidewall on each side of the center plane wherein a first portion18 s 1 of curved sidewall is proximate to the ABS, and a second portion18 s 2 is proximate to corner 18 c where the curved sidewall connectswith flared side 18 f of the main pole back portion. First portion 18 s1 forms an attack angle y from 0 to 40 degrees, and preferably 18-20degrees, with respect to center plane 44-44. In general, as the angle γincreases, the cross-track magnetic field gradient degrades. However, asangle γ approaches 0 degrees, the magnetic field from the main poledecreases dramatically. Therefore, we have found that γ=18 to 20 degreesis an optimum range to maintain an acceptable cross-track field gradientand magnetic field from the main pole. Preferably, a first portion ofside shield sidewall 19w that is a side gap distance d from firstportion 18 s 1 also is formed at the y angle with respect to the centerplane.

Side shields 19 s have a second sidewall portion 19 v facing the writepole and formed substantially conformal to curved sidewall portion 18 s2 up to height h1 of at least 80-100 nm where the sidewall 19 v nolonger follows the shape of the write pole and continues to an end 19 eat sides 60 (or 61) of the side shield. The closest approach of mainpole back portion 18 m to the ABS is at plane 46-46 that includescorners 18 c and is a second height h2 of >150 nm from the ABS. Curvedsidewall portion 18 s 2 and second sidewall portion 19 v that areproximate to corners 18 c form a maximum angle δ of about 60 degreeswith respect to center plane 44-44.

FIG. 2b depicts a down-track cross-sectional view of the trailing shieldand leading shield structure along center plane 44-44 in FIG. 2a . Themain pole has a tapered leading side 18 b 1 with a first end at the ABS30-30 and a back end at corner 18 g. A second leading side 18 b 2adjoins a dielectric layer 23, extends from corner 18 g toward a backend of the PMR writer, and parallel to plane 45-45 that is formedorthogonal to the ABS. The main pole also has a tapered trailing side18t1 between the ABS and corner 18 h. A second trailing side 18 t 2adjoins a dielectric layer 24, has a front end at corner 18 h andextends toward a back end of the PMR writer, and parallel to plane45-45. The leading shield 34 has a front side at the ABS, and a backside34 b at a height h5 from the ABS where the backside contacts dielectriclayer 23. Leading gap 17 a and write gap 17 b contact main pole sides 18b 1, 18 t 1, respectively.

Write gap 17 b preferably has a uniform thickness in a down-trackdirection, is formed between a tapered section 20 a 1 of the trailingshield hot seed layer and main pole trailing side 18 t 1, and has a backside that adjoins a front side of insulation layer 24. Tapered section20 a 1 has a front side at the ABS 30-30, a back side 20 s 2 at heighth, and a main pole facing side 20 s 1 separated from trailing side 18 t1 by write gap thickness a, and that is substantially parallel to themain pole tapered trailing side. A second section 20 a 2 of the trailingshield hot seed layer 20 a from FIG. 1 adjoins the back side of taperedsection 20 a 1 at height h, has a back side that adjoins an ABS facingside of non-magnetic layer 24 at height h6, and has a tapered side 20 s3 facing the main pole and offset therefrom by a down-track distance of(a+t), and having a lengthwise dimension (h6−h) along the x-axis that isparallel to plane 45-45. When t>0, coupling and internal flux leakagefrom the main pole to trailing shield is reduced compared with acondition where t=0. In the exemplary embodiment, the back side ofsecond section 20 a 2 is formed at the same height h6 as the back side20 e of the second magnetic layer 20 b in the trailing shield. Taperedsection 20 a 1 has a down-track distance (s+t) while section 20 a 2 hasa down-track thickness s.

We have discovered that increasing the write pole curvature in FIG. 2aand moving a front side of main pole back portion 18 m between corners18 c substantially closer to the ABS than in the POR design leads toreduced main pole to side shield flux shunting and enhanced cross-trackgradient. Curvature is defined as the difference in angles γ and δ,which is a maximum of around 60 degrees in the POR design, and typicallyabout 30-40 degrees when γ is 18 degrees and δ is in a range of 45 to 60degrees. Previous attempts to move corners 18 c closer to the ABSinvolved enlarging the attack angle γ, which causes unacceptabledegradation in cross-track field gradient. Greater curvature in thewrite pole sides in the present disclosure is achieved by reducing sideshield height in a first side facing the write pole, and including asecond side in each side shield that is formed essentially parallel tothe ABS and connected to an end of the first side as explained in afirst embodiment illustrated in FIG. 3. As a result, there is lesscoupling between side shields and the main pole than in the POR designwhich reduces internal flux shunting and improves writability(overwrite). Furthermore, the first embodiment enables more main polevolume within 150 nm of the ABS while maintaining an acceptable y angleto enhance the cross-track field gradient (TPI capability).

Referring to FIG. 3, a first embodiment of the present disclosure isillustrated where main pole flared sides 18 f and the first portion 18 s1 of curved write pole sidewall are retained from the POR design in FIG.2a . It should understood that the ABS view of the first embodiment isthe same as in FIG. 1 except for replacing side shields 19 s with sideshields 19 s 1. Moreover, the down-track cross-sectional view alongplane 44-44 of the first embodiment structure is the same as depicted inFIG. 2b . One key feature of the first embodiment of the presentdisclosure shown in FIG. 3 is a modified side shield 19 s 1 on each sideof the center plane 44-44. In particular, each side shield has a firstsidewall section 19 n 1 proximate to the ABS 30-30 and substantiallyconforming to the shape of first curved sidewall portion 18 s 1 alignedat angle γ with respect to the center plane. Angle γ is also referred toas the attack angle and is between 0 and 40 degrees, and preferably from18 to 20 degrees. Thus, first sidewall section 19 n 1 has a front end atthe ABS, and is separated from first portion 18 s 1 of curved write polesidewall by side gap distance d up to a height h3 that is 30-80 nm fromthe ABS, and significantly less than h1 in the POR design. A back end ofthe first sidewall section is at height h3. The side gap distance d is across-track width in the range of 20 to 60 nm. Each side shield has asecond sidewall section 19 n 2 formed substantially parallel to the ABSat height h3, and having a cross-track width c of 20 to 300 nm, andpreferably 20-100 nm, between the back end of the first sidewall sectionand a third sidewall section 19 n 3. If c>300 nm and h3<80 nm, then theside shield could become saturated with loss in TPI. The third sidewallsection extends to a far end 19 e at a side 60 (or 61) of the sideshield where the far end is a greater distance than h3 from the ABS.Each third sidewall section preferably forms an angle α of 20 to 60degrees with respect to plane 42-42 which includes second sidewall 19 n2. Throat height in the write pole 18 p is the distance along centerplane 44-44 between the ABS and plane 42-42.

A second key feature of the first embodiment is greater curvature in thecurved write pole sidewall compared with the design in FIG. 2a that isenabled by reducing the height of the first sidewall section 19 n 1 toh3, and by including second sidewall section (side) 19 n 2 as describedpreviously. As a result, there is a second portion 18 s 3 of curvedwrite pole sidewall formed proximate to corner 18 c 1 that issubstantially parallel to side 19 n 2 and at an angle θ of preferably90±5 degrees with respect to center plane 44-44. Greater curvature inthe write pole sidewall, expressed here as (θ−γ) with a maximum value inthe range of 90-95 degrees, and typically around 70 degrees, allowscorners 18 c 1 to be at a height h4 of 80 to 150 nm from the ABS, asubstantial reduction from height h2 of corners 18 c in the POR design.In the exemplary embodiment, side gap 17s is substantially uniform sincethere is a distance d between sidewall portion 18 s 3 and secondsidewall section 19 n 2.

FIG. 4 shows a top-down view of the overlay of the main pole and sideshield structure of the present disclosure with the main pole and sideshield of the POR design from FIG. 2a . Note that flared main polesidewalls 18 f are shared by both designs. However, in other locations,solid lines represent the first embodiment from FIG. 3 and dashed linesrepresent the FOR design from FIG. 2a . First, there is clearly moremain pole volume closer to the ABS in the first embodiment structure asindicated by regions 52 between write pole curved sidewall portions 18 s3 and 18 s 2. The area of regions 52 between the two curves represents aportion of the main pole that is moved closer to the ABS in the presentdisclosure, and is responsible for better overwrite in the firstembodiment design.

A second advantage of the first embodiment is less side shield volume inside shields 19 s 1 than in side shields 19 s that minimizes internalflux leakage from the main pole to side shields. The greater distancebetween the ABS and corners 18 c than between the ABS and corners 18 c 1along the curved write pole sidewall means there is less coupling (lessflux leakage) in region 50 where side shield 19 s 1 (sections 19 n 1+19n 2 in FIG. 3) follows the contour of the curved write pole sidewallthan in region 51 where side shield 19s (sections 19 w+19 v in FIG. 2a )follows the contour of the curved write pole sidewall. In other words,region 50 is considerably smaller than region 51 and this area reductionleads to less coupling since smaller area is directly related to lesscoupling when the side gap distance d is held constant.

We disclosed in related U.S. Pat. No. 9,361,912 (illustrated in FIG. 5therein) a PMR writer with a composite side shield structure that may beemployed to further improve overwrite, especially at side shield heightsless than 150 nm. Each side shield has a high saturation magnetization(hot seed) layer made of 19-24 kG material formed at an interface withthe side gap, and a second magnetic (10-16 kG) layer adjoining a side ofthe hot seed layer that is opposite the side gap. Furthermore, theleading shield preferably has an uppermost hot seed layer thatinterfaces with the lead gap and connects with the side shield hot seedlayers, and a lower magnetic layer made of 10-16 kG material thatadjoins the second magnetic layers in the side shields. As a result,when side gap d is reduced to a 20-60 nm range, and side shield heightis decreased to 0.15 micron or less, side shield saturation may beprevented while writability is maintained or enhanced.

Referring to FIG. 5, an ABS view of a modified AWA shield structurefabricated by the inventors is shown and is formed according to a secondembodiment of the present disclosure. The trailing shield design fromFIG. 1 is retained However, the side shields and leading shield areconfigured to include a hot seed layer that interfaces with side gaps 17s and leading gap 17 a, respectively. There is a leading shield hot seedlayer 34 h formed with a top surface 34 w along a plane 43-43 thatincludes a bottom surface of the leading gap 17 a and a top surface 34 tof side portions of the leading shield layer 34. Hot seed layer 34 h isaligned below the write pole leading edge 14 b, and has bottom surface34 b. Thus, the leading shield is considered to be a composite with alower magnetic layer 34 made of a 10-16 kG material, and an upper hotseed layer 34 h made of a 19-24 kG material wherein the latter has asubstantially smaller cross-track width than the former. All shieldlayers and the main pole may be selected from one of CoFeN, CoFeNi,NiFe, or CoFe.

Adjoining both ends of the hot seed layer 34 h at a top surface formedalong plane 43-43 is a side shield hot seed layer 19 h that ispreferably comprised of the same material and with a cross-track widthw1 that is equal to the down-track thickness of the leading shield hotseed layer. Hot seed layer 19 h has a bottom surface at plane 43-43 anda top surface at plane 41-41 which includes the write pole trailing edge14 t at the ABS. Each hot seed layer 19 h has an inner side 19 n 1facing a write pole side edge 14 s and adjoining side gap 17 s, and hasan outer side 19 m facing away from the side gap and adjoining a sideshield layer 19 s 1. Preferably, both sides 19 n 1, 19 m are alignedsubstantially parallel to a nearest write pole side edge 14 s.Therefore, each side shield is considered to be a composite with an“inner” hot seed layer 19 h, and an “outer” shield layer 19 s 1 made ofa 10-16 kG material. Preferably, thickness w1 is from 10 to 100 nm, andmore preferably, is from 20 to 60 nm. According to the exemplaryembodiment, side shield hot seed layers 19 h are not magneticallycoupled to the trailing shield hot seed layer 20 a. In otherembodiments, w1 may be increased and the write gap may have a narrowercross-track width than hot seed layer 20 a such that the trailing shieldhot seed layer contacts plane 41-41 adjacent to the write gap therebyallowing the hot seed layers 19 h to partially or fully contact hot seedlayer 20 a.

Referring to FIG. 6, a top-down view of the main pole and composite sideshield structure from FIG. 5 is shown with the write gap and trailingshields removed. The configuration from FIG. 2a is retained except forthe side shield structure wherein hot seed layer 19 h is insertedbetween side shield layer 19 s 1 and side gap 17 s. In one embodiment,hot seed layer 19 h has a cross-track width where w1 corresponds to thecross-track width c of side 19 n 2. Thus, outer side 19 m may be aligneddirectly below corner 18 c 1. In other embodiments, cross-track width cmay be increased so that a far end of side 19 n 2 that intersects withouter side 19 m is extended towards side 60 (or 61), and is a greaterdistance from center plane 44-44 than corner 18 c 1. In the exemplaryembodiment, sides 19 n 1, 19 n 2 are part of hot seed layer 19 h, andside 19 n 3 is part of side shield layer 19 s 1.

FIG. 7 depicts a down-track cross-sectional view along plane 44-44 inFIG. 5 and retains the features of FIG. 2b except leading shield hotseed layer 34 h is inserted between leading gap 17 a and leading shield34 from the ABS 30-30 to height h5. Hot seed layer 34 h has side 34 wadjoining the leading gap and side 34 v that faces away from the leadinggap and adjoins the leading shield. Preferably, sides 34 w, 34 v aresubstantially parallel to tapered main pole leading side 18 b 1.

To further demonstrate the advantages of the present disclosure, afinite element method (FEM) simulation was performed where a PMR writerwith the POR design in FIG. 1 and FIGS. 2a -2b has the followingdimensions: d=40 nm, γ=18 degrees, δ=45 degrees, h1=130 nm, and h2=180nm. The FOR design was compared with a PMR writer having a main pole andside shield design formed according to the first embodiment and shown inFIG. 3 where d=40 nm, c =60 nm, γ=18 degrees, θ=90 degrees, h3=50 nm,and h4=90 nm. The side shield structure and main pole in the FOR designare made of the same 10-16 kG and 19-24 kG materials, respectively, asin the side shield and main pole configuration of the first embodiment.

In FIG. 8, improved writability for the first embodiment configurationis illustrated on a graph of Hy_max Oe vs. erase width during AC mode(EWAC) where results from the main pole and AWA shield of the presentdisclosure are plotted along line 60 and have higher values for Hy (Oe)at each EWAC Value in nm than the FOR design with points along line 61.

FIG. 9 shows an improved cross-track field gradient for line 70representing results from the first embodiment configuration comparedwith line 71 representing the POR design. Hy_grad_x results are plottedvs. EWAC (nm).

The present disclosure also encompasses a method of forming a PMR writerwhere a first side shield side facing the write pole proximate to theABS has a height from 30 to 80 nm, the side shield has a second sideformed parallel to the ABS, and where the curved write pole sideproximate to a main pole corner has a sidewall portion formed at a 90±5degree angle with respect to a center plane aligned orthogonal to theABS. FIGS. 10-17 depict a sequence of steps whereby the main pole andside shield structure of the first embodiment are fabricated.

Referring to FIG. 10, leading shield 34 is formed on a dielectric layer23 by a conventional method. Then, magnetic layer 19 is plated on theleading shield. A photoresist layer 50 is coated and patternwise exposedthrough a photomask, for example, that may comprise opaque chromefeatures on a transparent quartz substrate. The photolithography processforms an opening 49 with sidewalls 50 s 1 on each side of the centerplane 44-44 which exposes a portion of magnetic layer top surface 19 t.

In FIG. 11, the photomask 55 is overlaid on the photoresist layer (notshown) during the exposure step in the photolithography process. Thephotomask comprises a transparent region 55 t and a pattern of opaquefeatures 55 n that are bounded on one side by sidewalls 55 s 1 formedpreferably at angle γ with respect to a center plane 44-44 that willbisect the main pole to be plated in a subsequent step. Sidewalls 55 s 1will determine the position of sidewalls 50 s 1 after the patternwiseexposure and a typical aqueous base development step. Likewise, theopaque photomask features have a second side 55 s 3 with a far end 55 eon each side of the center plane. Sides 55 s 3 will determine theposition of sidewalls 19 n 3 to be formed in each side shield 19 s 1. Athird side 55 s 2 for each opaque photomask feature is connected to anear end of side 55 s 3, is formed orthogonal to the center plane, andis aligned above where sidewall 19 n 2 will be formed in each sideshield. A key feature is the use of an opaque or partially opaque OPCshape 55 c on each side of the center plane, and at an intersection ofside 55 s 2 and side 55 s 1. Each OPC shape is preferably rectangularwith a cross-track width f, and a height r along the x-axis direction.The OPC shapes are advantageously employed to provide corners 50 p withessentially no rounding at the intersection of sides 50 s 3 and 50 s 1in the patterned photoresist layer 50 shown in FIG. 12. In the priorart, the absence of OPC shapes leads to considerable rounding in side 19w (FIG. 2a ) and a continuously curved side shield sidewall (19 w+19 v)after a subsequent etching step.

Referring to FIG. 12, a top-down view of the patterned photoresist layer50 from FIG. 10 is illustrated. As mentioned previously, OPC shapes inthe photomask are used to form a photoresist side 50 s 2 on each side ofthe center plane that is essentially parallel to the ABS 30-30, andintersects with a photoresist side 50 s 1 to form a corner 50 p wheresides 50 s 1, 50 s 2 intersect. Side 50 s 3 connects with a far end ofside 50 s 2 and extends to end 50 e above where side 60 (or 61) isformed in the side shield. Preferably, each side 50 s 2 has across-track width c corresponding to the cross-track width of side 19 n2 in each side shield 19 s 1 at the completion of the fabricationsequence.

In FIG. 13, a conventional etch process such as an ion beam etch (IBE)is employed to transfer the opening in the photoresist pattern (maskinglayer) through the magnetic layer 19 and stop on leading pole layer 34.The masking layer is then removed by a well known method. As a result,sides 19 n 1, 19 n 2, 19 n 3 are formed by way of their alignment belowsides 50 s 1, 50 s 2, 50 s 3, respectively, during the etch process.Side 19 n 2 is at a height h3 from the eventual ABS 30-30. Typically,height h5 of the underlying leading shield 34 is less than h3 such thatthe leading shield is covered by the side shields and is not visiblefrom a top view at this point. Dielectric layer 23 adjoins sides 19 n1-19 n 3.

FIG. 14 shows an ABS view of the structure in FIG. 13. A portion of topsurface 34 t of the leading shield is exposed between sides 19 n 1 andbelow opening 49′. Side shields 19 s 1 are formed from magnetic layer 19in FIG. 10 and have a top surface 19 t.

Thereafter, in FIG. 15, gap layer 17 is conformally deposited on sideshields 19 s 1 and on leading shield top surface 34 b. Opening 49 a isformed between the side shields and in the gap layer. The gap layer maycomprise two or more layers such as an inner Ru layer and an outerdielectric layer contacting each side shield. The outer dielectric layer(not shown), dielectric layer 23, and dielectric layer 24 (not shown)may be comprised of alumina, or other insulation materials used in theart.

In FIG. 16, the main pole layer 18 is plated to fill the opening 49 aand typically covers the top surface 19 t of the side shields 19 s 1.Next, as depicted in FIG. 17, a chemical mechanical polish (CMP) processmay be performed to form a trailing edge 14 t along plane 41-41 thatalso includes a top surface of each side shield 19 s 1 and a top surface17 t of each side gap 17 s. Note that side gaps 17 s and leading gap 17a are formed from gap layer 17. The main pole becomes the write pole 14at the eventual ABS. A conventional process may be used to form a taperon the trailing main pole side including the write pole at this point inthe fabrication.

The write gap and composite trailing shield are then formed on the mainpole including write pole 14, side gaps 17 s, and side shields 19 s 1 bya conventional process to complete the AWA shield structure shown inFIG. 1 from an ABS view, and the side shield structure in FIG. 3according to a top-down view. A lapping process is generally performedafter all layers in the PMR writer are formed to generate the ABS 30-30in FIG. 3.

The PMR writer of the present disclosure may be used in conventionalmagnetic recording (CMR) and SMR applications. Although the exemplaryembodiments depict an all wrap around shield structure, the main poleand side shield structure of the embodiments disclosed herein may alsobe employed in a partially wrapped around shield structure wherein theleading shield is removed as we have described in related U.S. Pat. No.9,299,367. The partially wrapped around shield design provides forreduced flux leakage from main pole to side shields, improveswriteability as well as cross-track and down-track field gradientsthereby enabling side gap and write gap dimensions 5-10 nm smaller thantypical writers for conventional and shingled magnetic recording.

While the present disclosure has been particularly shown and describedwith reference to, the preferred embodiment thereof, it will beunderstood by those skilled in the art that various changes in form anddetails may be made without departing from the spirit and scope of thisdisclosure.

We claim:
 1. A perpendicular magnetic recording (PMR) writer,comprising: (a) a main pole with a leading edge at an air bearingsurface (ABS) and formed at a first plane, and a trailing edge at theABS and formed along a second plane where the first and second planesare parallel to each other and are orthogonal to the ABS, and to acenter plane formed equidistant between two main pole sides that connectthe leading edge to the trailing edge; (b) a gap layer surrounding themain pole at the ABS and comprising a write gap that contacts thetrailing edge and has a first cross-track width, and a side gap layeradjoining the main pole sides and leading edge; (c) a composite sideshield at the ABS and on each side of the center plane, comprising; (1)a 19-24 kG magnetic (first hot seed) layer with an inner sidewalladjoining the side gap layer and facing a write pole portion of the mainpole, a second sidewall formed parallel to the ABS at a first heighttherefrom, and an outer side facing away from the write pole portion andadjoining a 10-16 kG magnetic layer; and (2) the 10-16 kG magnetic layerthat has a third sidewall connected to an end of the second sidewall,the third sidewall has a far end at a side of the composite side shield;and (d) a composite trailing shield at the ABS and comprising: (1) asecond 19-24 kG hot seed layer formed on a top surface of the write gap,and a 16-19 kG magnetic layer that adjoins a top surface and sidewallsof the second hot seed layer, and contacts a top surface of each 10-16kG magnetic layer at the second plane, and wherein the write poleportion of the main pole has a curved side on each side of the centerplane, each curved side extends from the ABS to a corner where thecurved write pole side adjoins a flared side of a main pole backportion, a first portion of each curved side proximate to the ABS isformed at the first angle γ with respect to the center plane, and asecond portion of each curved side proximate to the corner has a secondangle θ of about 90±5 degrees with respect to the center plane whereθ>γ.
 2. The PMR writer of claim 1 further comprised of a leading shieldwith a top surface contacting a portion of the side gap layer below themain pole leading edge, the leading shield, side shields, and 16-19 kGmagnetic layer in the composite trailing shield form an all wrap around(AWA) shield structure.
 3. The PMR writer of claim 2 wherein the leadingshield is further comprised of a third 19-24 kG hot seed layer with atop surface that contacts a bottom surface of each first hot seed layer.4. The PMR writer of claim 1 wherein each of the first hot seed layershas a cross-track width of about 10 to 100 nm.
 5. The PMR writer ofclaim 1 wherein the first angle y is from 0 to 40 degrees.
 6. The PMRwriter of claim 1 wherein the first height is from 30 to 80 nm.
 7. ThePMR writer of claim 1 wherein the second sidewall has a cross-trackwidth of 20 to 300 nm.
 8. The PMR writer of claim 1 wherein the cornerwhere each curved side adjoins the main pole back portion is 80 to 150nm from the ABS.
 9. The PMR writer of claim 1 wherein the side gap layerhas a cross-track width from 20 to 60 nm.
 10. The PMR writer of claim 1wherein the far end of the third sidewall is a greater distance from theABS than the first height, and the third sidewall forms an angle ofabout 20 to 60 degrees with respect to a plane which includes the secondsidewall.